1. Field of the Invention
The present invention is related to a light-emitting device (LED) structure of and the manufacturing method thereof, and particularly to, a vertical GaN-based LED structure and the manufacturing method thereof. More particularly, the vertical LED structure is a completely vertical structure and has a larger lighting area and the corresponding manufacturing method may be simplified at the same time.
2. Description of Related Art
Light-emitting diodes (LEDs) have been widely known as useful lighting facilities and expected to become the most important and efficient ones. As we see, they have been founded useful in some important applications, such as communications and other areas, such as mobile phone and some appliances. Recently, there is a trend that further introducing LEDs to ordinary human living utilization, such as large panels, traffic lights and lighting facilities and the perspective thereof are looking good. Therefore, LEDs are increasingly playing an important role in our daily life and deserving more of our efforts.
However, brightness has always been the biggest issue in the field, which has been challenging the more practical uses of LEDs in human living utilization. For the recent years, many efforts have been thrown in to improvement of brightness of LEDs. However, the results are not satisfactory enough in quest of the LED-based lighting facilities, one of the reasons is that the n-electrode is in the way of the produced light when the light emits out of the device. In appreciating this, please refer to FIG. 15 illustrating a prior light-emitting device for a GaN based LED. In the figure, the light-emitting device has a substrate 90, mostly a sapphire. Over the substrate 90, a buffering layer 91, an n-GaN based layer 92, a multi-quantum well (MQW) layer 93, a p-GaN layer 94 are formed in sequence. Next, an etching method is employed to form an exposing region 92a on the n-GaN based layer 92. Finally, the n-electrode 96 and p-electrode 95 are respectively formed on the desirable area (shown in FIG. 1). In the n-electrode's view, the light-emitting device structure is not completely a pure vertical structure, which leads to a reduction of the lighting surface of the device.
However, at the same time, the n-electrode on a light-emitting device may not be omitted since an LED needs to work with an electric bias fed and the corresponding excitation, and hence the n- and p-electrodes are both indispensable. However, the n-electrode is a source of limiting the lighting area according to the state of the art, also described above, and hence one of the reasons limiting the luminous efficiency of the LED since the n-electrode may hinder the lighting area on the LED, which may be readily known through FIG. 15, through which the desired light is emitted. Therefore, the illumination produced by the LED has long been not enhanced with respect to the limited lighting area of the LED.
In response to the long existed problem requiring an efficient solution, it is desirable to set forth an LED structure that may not be limited in luminous efficiency by the indispensable n-electrode. To this end, the inventors of the present invention provide herein a novel LED structure. In achieving such useful structure, a particular manufacturing method is needed and will also be set forth in the present invention.